A driver-side air bag device, which is installed in the center of a steering wheel, comprises a retainer, an air bag attached to the retainer, a gas generator (inflator) for deploying the air bag, and a module cover covering the air bag. Once a vehicle comes into collision, the inflator generates gases so that the air bag tears the module cover and is developed into a cabin of the vehicle.
A passenger-side air bag device which is installed in an instrument panel comprises a container, an air bag and an inflator which are mounted to the container, and a module cover attached in such a manner as to cover an opening of the container. Such a module cover is also sometimes called as a lid or a deployment door. In the event of a vehicle collision, the inflator operates to deploy the air bag and the module cover is pushed by the deployed air bag to open into a cabin so that the air bag is deployed widely.
The air bags are made of cloth. An air bag made by coating silicone rubber on textile of synthetic fiber such as polyester and polyamide is disclosed in JPA 63-78744 and JPA 2-270654. An air bag made by coating silicone emulsion composite or silicone latex composite as a treating composite which does not contain organic solvent in terms of working surroundings on the textile is described in JPA 56-16553, JPA 54-131661, JPA 5-98579, and U.S. Pat. No. 3,817,894.
These air bags are insufficient for the adhesion between the textile and the coating fluid, because coatings are applied to textile of synthetic fiber as to all of them. The air bags need measures, such as sticking tape made of rubber or silicone rubber on a sew-made part, to add the tearing strength and also improve the gastightness of the sew-made part. The air bags take long time to be sewed so that they are economically disadvantageous.
An air bag made of thermoplastic elastomer such as thermoplastic polyurethane disclosed in JPA 4-266544 are capable of fusing by heat so that they are advantageous over the conventional air bags made by coating rubber on textile of synthetic fiber and sewing in that sewing is not necessary.
However the air bag made of thermoplastic elastomer does not always expand quickly over a wide range of temperature, i.e. from very low temperature to high temperature (for example, from -40.degree. C. to +100.degree. C.)
An air bag is accommodated in the folded state in an air bag device, so that a sheet of the air bag made of a certain material sometimes adhere to each other at a portion where the sheets are in contact, resultiny that the portions will remain folded or will be broken due to tackiness or blocking thereof when the air bag expands.